NONEQUILIBRIUM AIR CLATHRATE HYDRATES IN ANTARCTIC ICE - A PALEOPIEZOMETER FOR POLAR ICE CAPS

Citation
H. Craig et al., NONEQUILIBRIUM AIR CLATHRATE HYDRATES IN ANTARCTIC ICE - A PALEOPIEZOMETER FOR POLAR ICE CAPS, Proceedings of the National Academy of Sciences of the United Statesof America, 90(23), 1993, pp. 11416-11418
Citations number
14
Categorie Soggetti
Multidisciplinary Sciences
ISSN journal
00278424
Volume
90
Issue
23
Year of publication
1993
Pages
11416 - 11418
Database
ISI
SICI code
0027-8424(1993)90:23<11416:NACHIA>2.0.ZU;2-#
Abstract
''Craigite,'' the mixed-air clathrate hydrate found in polar ice caps below the depth of air-bubble stability, is a clathrate mixed crystal of approximate composition (N2O2).6H2O. Recent observations on the Byr d Station Antarctic core show that the air hydrate is present at a dep th of 727 m, well above the predicted depth for the onset of hydrate s tability. We propose that the air hydrate occurs some 100 m above the equilibrium phase boundary at Byrd Station because of ''piezometry''-i .e., that the anomalous depth of hydrate occurrence is a relic of a pr evious greater equilibrium depth along the flow trajectory, followed b y vertical advection of ice through the local phase-boundary depth. Fl owline trajectories in the ice based on numerical models show that the required vertical displacement does indeed occur just upstream of Byr d Station. Air-hydrate piezometry can thus be used as a general parame ter to study the details of ice flow in polar ice caps and the metasta ble persistence of the clathrate phase in regions of upwelling blue ic e.